A core idea of the Multipath Transmission Control Protocol (MPTCP) is to add, between an application layer and a transmission layer, an MPTCP layer supporting multipath transmission. Conventional transmission control protocol (TCP) data is split into multiple TCP subflows, and different TCP subflows are transmitted along different paths and aggregated on a peer host. Although an MPTCP technology allows a terminal to simultaneously use multiple interfaces to perform communication, MPTCP requires that two parties participating in communication should both support MPTCP. When a communication party does not support MPTCP, MPTCP cannot be used to perform communication. Communication over MPTCP requires that two communication parties should both support the MPTCP protocol. In order that a host having an MPTCP capability can communicate with a host not having an MPTCP capability, a concept of an MPTCP proxy is further put forward. A final objective of the MPTCP proxy is to implement mapping between an MPTCP session and a TCP session, between a host supporting MPTCP and a host not supporting MPTCP. After the MPTCP proxy receives an MPTCP connection setup request initiated by the host supporting MPTCP, the MPTCP proxy uses an IP address that is of the host supporting MPTCP and is carried in the connection request to set up a TCP connection to the host not supporting MPTCP. An MPTCP connection setup process is similar to a TCP connection setup process. A difference lies in that MPTCP defines a new TCP option (MP_CAPABLE), used to indicate that the connection setup process is to set up an MPTCP connection. If MPTCP is not supported, a communication peer end ignores the MP_CAPABLE, and returns an ordinary TCP handshake message. Therefore, the host supporting MPTCP may determine whether the communication peer end supports MPTCP, and set up the MPTCP connection if the communication peer end supports MPTCP, or set up an ordinary TCP connection if the communication peer end does not support MPTCP. A function of the MPTCP proxy is to return, in place of the host not supporting MPTCP, the MP_CAPABLE to the host supporting MPTCP, so that the host supporting MPTCP considers that the communication peer end is a host supporting MPTCP, and further that the MPTCP connection may be set up.
In a mechanism of the conventional MPTCP proxy, an internet protocol (IP) address of a first MPTCP subflow of the host supporting MPTCP is used to set up a TCP session. However, when the host supporting MPTCP stops using an interface corresponding to the IP address, it is possible that the IP address is released or occupied by another host. This affects communication of the TCP session that is set up between the MPTCP proxy and the host not supporting MPTCP.